Found in yogurt, kefir and fermented foods, and described by the World Health Organization (WHO) as "live micro-organisms which when administered in adequate amounts confer a health benefit on the host," probiotics are believed to enhance the defensive action of the cells that line the gut by stimulating healthy immune function and by inhibiting the growth of viral and bacterial pathogens.

Regarding the new study, Cabana noted, one theory is that the absence of infectious exposure at a critical point in immune system development leads to a greater risk for eczema and asthma.

Additionally, lack of key bacteria in the infant intestinal microbiota has been associated with the later increased risk of allergic disease.

Therefore, supplementing with specific probiotic strains may modify the entire microbiota community patterns and decrease this risk.

However, in an editorial titled "Probiotics in the Child Care Center: Context Matters" and published in the same issue of Pediatrics, Cabana and Daniel Merenstein of Georgetown University Medical Center in Washington, D.C. suggest that as breast milk contains natural compounds that act like prebiotics, the best source of influencing a child's gastrointestinal tract is breast milk.